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<title>Section 13.1.&nbsp; Introduction</title>
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<h3 class="docSection1Title" id="454331-801">13.1. Introduction</h3>
<p class="docText"><a name="idd1e94532"></a><a name="idd1e94537"></a><a name="idd1e94540"></a><a name="idd1e94545"></a><a name="idd1e94550"></a><a name="idd1e94555"></a><a name="idd1e94560"></a>Daemons are processes that live for a long time. They are often started when the system is bootstrapped and terminate only when the system is shut down. Because they don't have a controlling terminal, we say that they run in the background. UNIX systems have numerous daemons that perform day-to-day activities.</P>
<p class="docText">In this chapter, we look at the process structure of daemons and how to write a daemon. Since a daemon does not have a controlling terminal, we need to see how a daemon can report error conditions when something goes wrong.</P>
<blockquote>
<p class="docText">For a discussion of the historical background of the term <span class="docEmphasis">daemon</span> as it applies to computer systems, see Raymond [<a class="docLink" href="bib01.html#biblio01_053">1996</a>].</p>
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